Growth and recruitment of lake trout juveniles in Lake Champlain

Session: Restoration and Management of Great Lakes Fishes (1)

Pascal Wilkins, University of Vermont, [email protected]
J. Marsden, University of Vermont, Rubenstein School of Environment and Natural Resources, [email protected]

Abstract

Lake trout were extirpated from Lake Champlain by 1900 and have been stocked annually since 1973, with no wild recruitment seen until 2015. Lake trout stocked in fall as fingerlings (age-0) are the size of age-1 wild fish and have high recruitment, so age-0 growth and overwinter survival to age-1 are likely key parameters for wild lake trout recruitment. We hypothesized that for lake trout, a coldwater species, feeding may not stop in winter and overwinter growth could be a period of continued growth. To evaluate year class abundance, size, and condition of yearling and older year classes, we sampled with a bottom trawl every 2-3 weeks throughout the ice-free season, 2015-2018, in Lake Champlain. Length-frequency data of wild recruits identified four size classes, equivalent to ages-0 through age-3, that fully recruited to the sampling gear. Relative abundance and proportion of juvenile wild lake trout increased annually during the sampling period. Wild lake trout grew in length overwinter while condition remained stable in most cohorts, indicating juveniles actively foraged during the winter. Our results show that abundance of wild juvenile lake trout is increasing in Lake Champlain, and suggest that overwinter foraging could be a key to recruitment.